Combine arrays that have same value - php

Question

I have array like this
$arr=[["a","b"],["b","c"],["d","e"],["f","c"]];
if sub arrays share same value they should be be merged to one array
expected output:
$arr=[["a","b","c","f"],["d","e"]];
I`m trying to avoid doing foreach inside foreach for solving this.

Answer 1

It seems your inner arrays always have 2 items. so nested loops aren't necessary. Here is a solution which I originally wrote in JS but it should work just as good and most efficient in PHP:
$arr=[["a","b"],["b","c"],["d","e"],["f","c"],["h","e"]];
$output = [];
$outputKeys = [];
$counter = 0;
foreach($arr as $V) {
if(!isset($outputKeys[$V[0]]) && !isset($outputKeys[$V[1]])) {
$output[$counter] = [$V[0], $V[1]];
$outputKeys[$V[0]] = &$output[$counter];
$outputKeys[$V[1]] = &$output[$counter];
$counter++;
}
elseif(isset($outputKeys[$V[0]]) && !isset($outputKeys[$V[1]])) {
array_push($outputKeys[$V[0]], $V[1]);
$outputKeys[$V[1]] = &$outputKeys[$V[0]];
}
elseif(!isset($outputKeys[$V[0]]) && isset($outputKeys[$V[1]])) {
array_push($outputKeys[$V[1]], $V[0]);
$outputKeys[$V[0]] = &$outputKeys[$V[1]];
}
}
var_dump($output); // [["a","b","c","f"],["d","e","h"]]
DEMO (click the execute button)
Pointers are your friends. Use them :)

Answer 2

The following algorithm should do what you want. It simply checks through each item and checks if it already exists in the newly created array, and if it does it adds it to that item instead of a new one:
<?php
$arr=[["a","b"],["b","c"],["d","e"],["f","c"]];
$newArr = [];
foreach ($arr as $items) {
$newKey = null;
foreach ($items as $item) {
foreach ($newArr as $newItemsKey => $newItems) {
if (in_array($item, $newItems)) {
$newKey = $newItemsKey;
break 2;
}
}
}
if ($newKey !== null) {
$newArr[$newKey] = array_merge($newArr[$newKey], $items);
} else {
$newArr[] = $items;
}
}
$newArr = array_map('array_unique', $newArr);
print_r($newArr);
Output:
Array
(
[0] => Array
(
[0] => a
[1] => b
[3] => c
[4] => f
)
[1] => Array
(
[0] => d
[1] => e
)
)
DEMO

Answer 3

This is solution I get for now.
$arr=[["a","b","c","f"],["d","e"]];
$sortedArray = sortFunction($arr,0,array());
function sortFunction($old,$index,$new) {
if ($index == sizeof($old)) return $new;
for ($i = 0; $i<sizeof($new); $i++) {
if (count(array_intersect($new[$i],$old[$index]))) {
$new[$i] = array_unique(array_merge($old[$index],$new[$i]), SORT_REGULAR);
return sortFunction($old,$index + 1,$new);
}
}
$new[] = $old[$index];
return sortFunction($old,$index + 1,$new);
}